Southwest Airlines via DealBase discounts select nationwide 1-way fares, with prices starting from $48.98. That's the lowest price we could find for select routes by $18. Book this travel deal by June 6 for travel from August 20 through December 18. Buy Now Tips On the DealBase landing page, click on "Southwest Airlines" in the top line to see this sale. We found this price on flights departing on August 20 from Portland, OR (PDX) to Oakland, CA (OAK). All prices, dates, and booking details were valid at the time of publication.